This invention relates to needle-free injection devices and, more particularly, to a needle-free injection device that avoids potential contamination of the injected fluids.
Needles were originally used in the common medical practice of intravenously infusing various liquids into a blood vessel of a patient, performing series of injections into patients, taking blood samples, and the like. Needles, however, present a risk of passing blood borne pathogens to health care providers should they be inadvertently stuck by a used needle. Needle-free injection sites or valves were developed to eliminate the problems associated with the use of needles in medical procedures. The nature of the problem and the use of needle-free injection valves are discussed more fully in U.S. Pat. No. 5,006,114, whose disclosure is incorporated by reference. The ""114 patent also discusses several ways in which a connector may be made to eliminate the use of the needle.
Briefly, there are at least three major types of needle-free devices. The first is the split septum-type connector, which is accessed by a blunt cannula. The second is a sheathed needle. The third is a valve-type mechanism in which a standard male-to-female medical luer-friction connection is made between the outlet side of a syringe and the inlet side of a needle-free valve. When this connection is made, a piston is displaced from a closed to an open position, thereby allowing fluid to flow through the valve to the output side of the valve. The outlet side of the valve is connected through a male-to-female luer connection to a catheter that has been set in the patient. Once the fluid has been administered to the patient, the syringe is disconnected from the valve and the piston returns to its closed position to seal the injection valve. Examples of such valve-type mechanisms are found in U.S. Pat. Nos. 6,228,069; 6,245,048; and 5,439,451.
While such valve-type mechanisms provide an improvement over alternative approaches, the available valve-type mechanisms permit contamination of the sterile fluid being injected into the patient, with potentially highly injurious or even fatal results. There is a need for an improved approach to needle-free injection valves which avoid inadvertently drawing fluid out of the patient as a result of the deactivation of the valve, and also avoid contamination of the sterile fluid being injected. The present invention fulfills this need, and further provides related advantages.
The present invention provides a nonvented, needle-free injection valve. No needle is used in the valve or in the syringe used in the injection procedure. The needle-free injection valve includes a fluid capacitor that prevents injected fluid or bodily fluids from being drawn out of the injection location in the patient. The needle-free injection valve is sealed against intrusion of external fluids or gases into the interior of the valve, avoiding contamination of the sterile fluid being injected.
In accordance with the invention, an injection valve comprises a housing having an inlet, an outlet, and a fluid channel extending between the inlet and the outlet, and a bore within the housing. A piston is slidable within the bore between a first position and a second position and biased toward the first position. The piston closes and seals the inlet when the piston is in the first position, and allows fluid to pass from the inlet to the fluid channel to the outlet when the piston is in the second position. There is a piston seal between the piston and a wall of the bore. The piston seal divides the bore into a sealed chamber and an unsealed chamber. There is no vent between the sealed chamber and an exterior of the housing. Desirably, the bore is substantially cylindrical with a bore axis, and the inlet and the outlet are coaxial along the bore axis. The piston seal is preferably a sliding seal but it may be a diaphragm-type or other type of seal.
In an injection operation, the piston is initially in the first position and seals the inlet. To inject a sterile fluid into a patient, an end of a (needleless) syringe is inserted into the inlet, pushing the piston to the second position and unsealing the inlet. The syringe is operated to inject sterile fluid into the inlet, through the fluid channel, and out the outlet to a catheter inserted into the patient. Fluid enters the unsealed chamber during this injection procedure. When the injection is complete, the end of the syringe is withdrawn from the inlet. The piston moves back to the first position and seals the inlet. As the piston moves from the second position to the first position, sterile fluid is forced from the unsealed chamber through the fluid channel and out the outlet to the patient, preventing bodily fluids from being drawn out of the patient and back into the catheter and the injection valve. The injection valve works much the same for an aspiration, in which the inserted syringe end creates a partial suction to take blood from the patient through the catheter. In each case, it is conventional practice to inject a small amount of saline both prior to and after a fluid injection or aspiration.
In another embodiment, an injection valve comprises a housing having an inlet, an outlet, a fluid channel extending between the inlet and the outlet, and a bore within the housing, the bore having a closed end. A piston is slidable within the bore between a first position wherein the piston is relatively far from the closed end and a second position wherein the piston is relatively near to the closed end. The piston closes and seals the inlet when the piston is in the first position and allows fluid to pass from the inlet to the fluid channel to the outlet when the piston is in the second position. A biasing spring biases the piston toward the first position. A piston seal between the piston and a wall of the bore divides the bore into an unsealed chamber and a sealed chamber adjacent to the closed end. There is no vent between the sealed chamber and an exterior of the housing. Features discussed in relation to the other embodiments may be used with this embodiment.
In one version of this embodiment, a deformable membrane has a first side in communication with the sealed chamber. The deformable membrane is deformable responsive to gas pressure changes within the sealed chamber. In another version, a gas accumulator communicates with the sealed chamber. In another version, a gas pressure within the sealed chamber is less than a gas pressure within the unsealed chamber, when the piston is in its first position. These embodiments minimize any adverse affect on piston movement arising from the compression of the gas in the sealed chamber.
In a third embodiment, an injection valve comprises a housing having a body, an inlet tube at a first end of the body, an outlet tube at a second end of the body remote from the first end, and a fluid channel extending through the body and between the inlet tube and the outlet tube. Preferably, the inlet tube is sized to receive a syringe tip therein. There is a bore within the housing. The bore has a bore axis and a closed end adjacent to the second end of the body. The inlet tube is coaxial with the bore axis. A piston has a first axial segment coaxial with the bore axis and slidable within the bore between a first position wherein the first axial segment is relatively far from the closed end and a second position wherein the first axial segment is relatively near to the closed end. The piston further has a second axial segment coaxial with the bore axis and remote from the closed end of the bore. The second axial segment closes and seals the inlet tube when the first axial segment is in the first position and allows fluid to pass through the inlet tube when the first axial segment is in the second position. A biasing spring biases the piston toward the first position. A piston seal is positioned between the first axial segment of the piston and a wall of the bore. The piston seal divides the bore into a unsealed chamber and a sealed chamber adjacent to the closed end. There is no vent between the sealed chamber and an exterior of the housing. In all of the embodiments and versions, it is preferred that the inlet and the outlet are coaxial with the bore axis. Other features discussed in relation to the prior embodiment may be used with this embodiment.
In prior designs of needle-free injection valves, a vent is provided through the housing between the otherwise-sealed chamber defined at the otherwise-closed end of the bore, and the exterior of the housing. The resulting venting equilibrates the pressure in the sealed chamber and the external environment to minimize the possibility that gas could flow past the piston seal and into the fluid being injected. Thus, the vent is used to maintain ambient pressure in the sealed chamber to prevent gas from being driven across the piston seal and into the unsealed chamber. The pressure equilibration also avoids a back pressure on the piston that can interfere with its operation and makes the valves easier to operate. However, the presence of the vent creates other problems which have either not been appreciated or have been ignored as having no apparent solution. The vent is typically located in a relatively inaccessible location where it cannot be readily disinfected. Nonsterile gases or fluids from the external environment, and microorganisms that they carry, may enter the interior of the valve through the vent. Even though there is a sliding seal between the piston and the wall of the bore to define the sealed chamber, the nonsterile gases or fluids may find their way past this seal, as the piston is repeatably cycled along the bore axis, and into the sterile fluids being injected into the patient, thereby potentially contaminating the patient.
The present invention has no vent between the sealed chamber and the exterior of the housing. The absence of such a vent ensures that no contaminant may find its way into the sealed chamber and thence into the unsealed chamber and the sterile fluid. Pressure management between the sealed chamber and the unsealed chamber is accomplished in other ways, as described above, such as membranes, gas accumulators, or initial pressure control.
The present approach thus achieves a fluid-capacitor effect while ensuring that external contaminants cannot enter through a vent and find their way into the unsealed chamber and thence into the sterile fluid in the next injection cycle. Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The scope of the invention is not, however, limited to this preferred embodiment.